Energy efficient and fast charge modes of a rechargeable battery

ABSTRACT

A method of providing power to an electronic device in an energy-efficient manner includes transitioning between power states corresponding to charging and discharging a battery. The state of charge of the battery is detected. Upon detecting a high threshold state of charge, an external power source such as an AC-to-DC adapter is disabled, and the battery to provides primary power to the electronic device. Upon a low threshold state of charge, the AC-to-DC adapter is controlled to provide a high current output to charge the battery and provide primary power to the electronic device. The power states, when cycled over time based on the state of the battery, provide for an energy-efficient method of powering the electronic device.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/179,182, filed on May 18, 2009, the entire teachings of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The portable power industry has traditionally been using charge ratesbetween 0.7 C and 1 C when charging electronic devices, which is therate used for laptop computers. This current allows the notebookcomputer's battery pack to be charged at currents that are 70% to 100%of the value of rated capacity of the cells. For example, in a batterypack containing 18650 cells, rated at 2.2 Ah, in a 2p3s configuration(two cells in parallel, three cells in series), a charging current of 1C would be equivalent to a charging current of 4.4 A for the pack. Thischarging current is allowed until a maximum voltage (V_(max)) isreached, which is typically set at about 4.2V. Once V_(max) has beenreached, the current is lowered by control circuitry to disallow, inthis example, any of the three blocks of two parallel cells to reachvoltage levels higher than 4.2V. In addition to the current beinglimited, the charging rate is even slower once V_(max) has been reached.Electronic circuits managing this type of functionality are known in theart and have been implemented in battery packs for notebook computers.For a notebook computer, typical charging times are of several hours toreach a fully charged battery.

Safety and battery life are the main problems with providing fastercharging. Practically, for lithium ion (Li-ion) batteries during fastcharging, batteries may locally display overcharging, which may depositlithium onto the carbon anode. This lithium deposit lowers safety of thebattery, which may more easily go into thermal runaway, increase itsinternal gas pressure, and eventually explode. Another problem with fastcharging is the rapid change of electrode dimensions, such as thicknessvariation. Mechanical degradation of the electrode structure is fasterduring this relatively fast charge than what would be the case forslower charging. These limiting features concern all Li-ion batteries,more or less, depending on battery design. Batteries may be designed totake charge faster by limiting impact of detrimental aspects, such assafety and battery life.

However, for batteries having multiple cells in parallel, a particularconcern arises when trying to quickly charge battery packs. This concernhas to do with the imbalance of cells in parallel. Impedance andcapacity degradation is different between cells due to differencesbetween cells during manufacturing and environmental exposure aftermanufacturing (i.e., temperature, vibration, mechanical shock, etc.).This means that two cells, having initially similar conditions in termsof (i.e., capacity and impedance), will display different performanceafter a few months of use. Each block of parallel cells will be limitedby the weakest cell, having lowest capacity and/or highest impedance, asthis is the cell that will reach V_(max) earlier than the cell havingbetter characteristics. As cycling progresses, the weakest cell willdegrade even quicker, as it will always be the cell that experiences themost extreme conditions. Safety is also a concern as performance isdecreased. The cell having the lowest performance will normally be thecell having the highest chance of being overcharged, thereby being asafety concern.

SUMMARY OF THE INVENTION

Current notebook PCs and other battery powered devices do not provide amechanism for the user to activate an environment-conserving powerefficient charging and discharging mode of the battery pack, AC adapterand device. Furthermore, an economical communication method between thebattery pack, AC adapter and device does not exist to notify thesecomponents of the selected power state.

Current devices such as notebook PCs also do not provide a mechanism forthe user to activate an accelerated charging mode of the battery.Furthermore, the current required for such fast charging modes plusnormal system loads will often exceed the power capacity of a typical ACadapter and will require the notebook to reduce power consumption itselfin order to provide sufficient power for accelerated charging of thebattery.

Embodiments of the present invention enable energy efficient power modesand fast charging modes in a notebook PC or other battery-powereddevice, battery pack and AC adapter.

Embodiments of the present invention include methods of providing powerto an electronic device. Upon detecting a battery reaching a highthreshold state of charge, a first power state is entered by switching acircuit to disable current at an AC-to-DC adapter and enabling thebattery to provide primary power to the electronic device. Upondetecting the battery reaching a low threshold state of charge, a secondpower state is entered by switching the circuit to provide a highcurrent at the AC-to-DC adapter to charge the battery and provideprimary power to the electronic device. The first and second states,when cycled over time based on the state of the battery, may provide foran energy-efficient method of powering the electronic device byoperating the AC-to-DC adapter at a high efficiency through high currentoutput.

In further embodiments of the invention, the AC-to-DC adapter chargesthe battery at a high rate in the second power state, the high ratebeing greater than 1 C, 1.5 C or a greater multiple of 1 C dependent ona maximum safe charge rate of the battery. The battery may provide anindication of a maximum safe charge rate, which is detected and employedto select a current output of the AC-to-DC adapter. Further, the firstand second power states may be alternated over time in response todetecting the high and low threshold charge states of the battery.

In still further embodiments of the invention, the first and secondpower states can be enabled in response to a user selection of anenergy-efficient power mode to power the electronic device. Thisselection may be made among a plurality of different power and chargemodes, including a “normal” power mode and a “fast” charge mode. Suchmodes can include a power state in which a circuit is switched toprovide a low current at the AC-to-DC adapter to charge the battery at alow rate and provide primary power to the electronic device. The lowrate of charge may be less than 1 C, such as a typical charge rage of0.7 C. The higher current provided at the second power state may resultin a higher energy efficiency operation of the AC-to-DC adapter.

In still further embodiments of the invention, characteristics of theAC-to-DC adapter may be detected, including output current and anindication of efficiency at a given output current, to determine aselection of output current in the second power state. Characteristicsof the battery may also be detected to determine output current,including a maximum safe charge of the battery. The battery may be alithium ion (Li-ion) battery, in particular a Li-ion battery capable ofbeing safely charged at a rate greater than 1 C, 1.5 C or a multiple of1 C.

In still further embodiments of the invention, a plurality of AC-to-DCadapters may be selected to provide the high current in the second powerstate. Such a selection may be based on an indication of maximum outputcurrent at each of the plurality of AC-to-DC adapters. The selection mayfurther include power sources other than AC-to-DC adapters, such as aDC-to-DC adapter and an external battery. Selection among multiple powersources can be based on an indication of energy efficiency correspondingto a given current output at each of the power sources.

Further embodiments of the invention include an apparatus for providingpower to an electronic device. The apparatus may include a power circuitconfigured to enable and disable power to the electronic device from abattery and an AC-to-DC adapter. A power circuit is configured to enableand disable power to the electronic device from a battery and anAC-to-DC adapter. Further, a controller is coupled to the power circuitand configured to transition between first and second power states asdescribed above.

Still further embodiments of the invention may include a system forproviding power to an electronic device. The system may include abattery and an AC-to-DC adapter, each configured to provide power to theelectronic device, and a controller as described above to transitionbetween first and second power states.

Further embodiments of the invention may include an electronic devicethat includes a device housing and a charge storage power supply coupledto the device housing. Electronics in the device housing are powered bythe charge storage supply. A charge circuit has plural modes ofoperation to charge the charge storage power supply from an externalpower source at different charging rates. An actuated mode switchchanges charging rates of the charging circuit. In one embodiment theactuated mode switch accelerates charging rate. In another embodimentthe actuated mode switch decelerates charging rate. In still anotherembodiment, the actuated mode switch discharges the battery. Theactuated mode switch can be manually operated or it can operateautomatically.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingembodiments of the present invention.

FIG. 1 shows a functional block diagram of the electronic circuitry uponwhich the present embodiment may be implemented.

FIG. 2 illustrates a process flow diagram of an exemplary fast chargeprocess.

FIG. 3A illustrates a fast charge button and display on a battery packupon which the state-of-charge of a battery pack may also be shown.

FIG. 3B provides a close-up view of the aforementioned fast chargebutton and display on the battery pack of a portable device.

FIG. 4A illustrates a notebook computer with a “FAST CHARGE” buttonlocated on the keyboard.

FIG. 4B shows a close-up view of the “FAST CHARGE” button located on anotebook computer keyboard.

FIG. 4C shows an exemplary user interface display window that may appearto present a user with the option to initiate software that will performthe “fast charge” option of the portable device battery pack.

FIG. 5A is a block diagram of an electronic device and an associatedcharging system in which embodiments of the present invention may beimplemented.

FIG. 5B is a block diagram showing the system of FIG. 5A in furtherdetail.

FIG. 6 is a chart depicting a relation between power efficiency andoperating load of an AC power adapter.

FIG. 7 is a state diagram illustrating a plurality of modes for charginga battery.

FIG. 8A is a flow diagram illustrating a method of initiating anenergy-efficient charge mode.

FIG. 8B is a flow diagram illustrating a method of conducting anenergy-efficient charge mode with reference to the system of FIG. 5B.

FIGS. 9A-C are timing diagrams illustrating AC adapter current andbattery pack current during each of a plurality of charge modes.

DETAILED DESCRIPTION OF THE INVENTION

A description of example embodiments of the invention follows.

The teachings of all patents, published applications and referencescited herein are incorporated by reference in their entirety.

FIG. 1 illustrates a functional block diagram of the electroniccircuitry 100 in a battery pack as used in current practice upon whichthe present embodiment may be implemented. In FIG. 1, a multiple cellbattery 101 may be connected to an independent overvoltage protectionintegrated circuit (OVP) 102, an Analog Front End protection integratedcircuit (AFE) 104, and a battery monitor integrated circuitmicrocontroller (microcontroller) 106. One with skill in the art willunderstand that the present invention is not limited to theaforementioned electronic circuitry of the schematic illustrated in FIG.1.

The OVP 102 may allow for monitoring of each cell of the battery pack bycomparing each value to an internal reference voltage. By doing so, theOVP 102 may be able to initiate a protection mechanism if cell voltagesperform in an undesired manner, e.g., voltages exceeding optimal levels.The OVP 102 is designed to trigger the non-resetting fuse 110 if thepreset overvoltage value (i.e., 4.35V, 4.40V, 4.45V, and 4.65V) isexceeded for a preset period of time and provides a third level ofsafety protection.

The OVP 102 may monitor each individual cell of the multiple cellbattery 101 across the Cell 4, Cell 3 , Cell 2, and Cell 1 terminals(which are ordered from the most positive cell to most negative cell,respectively). The OVP 102 is powered by multiple cell battery 101 andmay be configured to permit cell control for any individual cell of themultiple cell battery 101.

The AFE 104 may be used by the system host controller to monitor batterypack conditions, provide charge and discharge control via charge FET 118and discharge FET 116 respectively, and to provide updates of thebattery status to the system. The AFE 104 communicates with themicrocontroller 106 to enhance efficiency and safeness. The AFE 104 mayprovide power via the VCC connection to the microcontroller 106 usinginput from a power source (e.g., the multiple cell battery 101), whichwould eliminate the need for peripheral regulation circuitry. Both theAFE 104 and the microcontroller 106 may have terminals, which may beconnected to a series resistor 112 that may allow for monitoring ofbattery charge and discharge. Using the CELL terminal, the AFE 104 mayoutput a voltage value for an individual cell of the multiple cellbattery 101 to the VIN terminal of the battery monitor integratedcircuit microcontroller 106. The microcontroller 106 communicates withthe AFE 104 via the SCLK (clock) and SDATA (data) terminals.

The microcontroller 106 may be used to monitor the charge and dischargefor the multiple cell battery 101. The microcontroller 106 may monitorthe charge and discharge activity using the series resistor 112 placedbetween the negative cell of the multiple cell battery 101 and thenegative terminal of the battery pack. The analog-to-digital converter(ADC) of the microcontroller 106 may be used to measure the charge anddischarge flow by monitoring the series resistor 112 terminals. The ADCof the microcontroller 106 may be used to produce control signals toinitiate optimal or appropriate safety precautions for the multiple cellbattery 101. If the microcontroller 106 detects abnormal or unsafeconditions it will disable the battery pack by triggering thenon-resetting fuse 110.

While the ADC of the microcontroller 106 is monitoring the voltageacross the series resistor 112 terminals, the microcontroller 106 (viaits VIN terminal) may be able to monitor each cell of the multiple cellbattery 101 using the CELL terminal of the AFE 104. The ADC may use acounter to permit the integration of signals received over time. Theintegrating converter may allow for continuous sampling to measure andmonitor the battery charge and discharge current by comparing each cellof the multiple cell battery 101 to an internal reference voltage. Thedisplay terminal of the microcontroller 106 may be used to run the LEDdisplay 108 of the multiple cell battery 101. The display may beinitiated by closing a switch 114.

The microcontroller 106 may be used to monitor the multiple cell battery101 conditions and to report such information to the host systemcontroller across a serial communication bus (SMBus). The SMBuscommunication terminals (SMBC and SMBD) may allow a system hostcontroller, SMBus compatible device, or similar device (hereinaftercalled “processor”) to communicate with the microcontroller 106. Aprocessor may be used to initiate communication with the microcontroller106 using the SMBC and SMBD pins, which may allow the system toefficiently monitor and manage the multiple cell battery 101. Theprocessor may be the microcontroller 106 itself and may contain internaldata flash memory, which can be programmed to include information, suchas capacity, internal reference voltage, or other similar programmableinformation.

The AFE 104 and microcontroller 106 provide the primary and secondarymeans of safety protection in addition to charge and discharge control.Examples of current practice primary safety measures include batterycell and pack voltage protection, charge and discharge overcurrentprotection, short circuit protection, and temperature protection.Examples of currently used secondary safety measures include monitoringvoltage, battery cell(s), current, and temperature.

The continuous sampling of the multiple cell battery 101 may allow theelectronic circuitry to monitor or calculate characteristics of amultiple cell battery 101, such as state-of-charge, temperature, charge,or the like. One of the parameters that is controlled by the electroniccircuitry 100 is the allowed charging current (ACC). An aspect of thedisclosed embodiments is to allow the user of a portable device to havethe option to control this parameter by selecting a fast or slowcharging mode. When selecting the mode of charging, the ACC parameterchanges in addition to other parameters necessary to control thecharging of the battery within safe limits. This allows a battery to beoptionally charged faster than what would have been traditionallyavailable. The user of the portable device may also control the chargemode by allowing the user to adjust the fast charge mode in steps (e.g.,normal, fast, super fast, ultra fast, etc.) or on a continuous scale(e.g., 1×, 2×, 3×, 4×, etc.). A user may prefer to have more controlover the fast charge mode parameter because such allows the user tobalance performance (i.e., battery cycle life) against charge tradeoffs.

The program stored for the battery monitor integrated circuitmicrocontroller 106 may be modified to implement the fast chargeindications described herein. The electronic circuit in FIG. 1 could beprogrammed with parameters suitable for the respective battery used inthe battery 101. Each battery manufacturer has unique chemistry andinterpretation of how the battery may be used in best mode to providelong cycle life, high capacity, and high safety. One with skill in theart will understand that a microcontroller used in accordance with thepresent invention is not limited to the design of FIG. 1.

It is preferred, though not required, that the cells in a multiple cellbattery 101 be in series due to different impedances of the cells.Impedance imbalance may result from temperature gradients within thepack and/or manufacturing variability from cell to cell. Two cellshaving different impedances may have approximately the same capacitywhen charged slowly. It may be seen that the cell having the higherimpedance reaches its upper voltage limit (V_(max)) in a measurement set(e.g., 4.2V) earlier than the other cell. If these two cells were inparallel in a battery pack, the charging current would therefore belimited to one cell's performance, which prematurely interrupts thecharging for the other cell in parallel. This degrades both packcapacity as well as pack charging rate. In order to avoid thesedetrimental effects, it is therefore preferred for the currentembodiments to utilize battery packs having only one cell or all cellsin series having a fast charge option. Such preferred configurations aredescribed in PCT/US2005/047383, and U.S. Provisional Application No.'s60/639,275; 60/680,271; and 60/699,285; which are hereby incorporated byreference in their entireties. A preferred battery is disclosed in aU.S. application Ser. No. 11/474,081 (U.S. Pub. 2007/0298314) for“Lithium Battery With External Positive Thermal Coefficient Layer,”filed Jun. 23, 2006, by Phillip Partin and Yanning Song, incorporated byreference in its entirety.

FIG. 2 illustrates a process flow diagram of an exemplary fast chargeprocess 200 where a user is presented with the option of choosing thenormal charge mode (Step 202) of the portable device battery pack. Ifthe user opts to use the fast charge mode (Step 204), the user can do sovia one of three mediums: a switch on the portable device (Step 206), aswitch on the battery pack (Step 207), or an icon on the portable devicedisplay control panel or menu (Step 208), any one ore more of which maybe available. From either of the three mediums, the user can initiatethe fast charge function (Step 210). The initiation of the fast chargefunction (Step 210) can be done either by an alternate firmware settingin the charging battery monitor integrated circuit microcontroller 106(Step 212) or the logic and charging circuits for fast charging (Step214). The alternate firmware setting in charging the battery monitorintegrated circuit microcontroller 106 (Step 212) then uses the logicand charging circuits for fast charging (Step 214). After using thelogic and charging circuits for fast charging (Step 214), the processwill display the charge status to the user (Step 216), which can occurin one of the following mediums: an icon on the portable device controlpanel or menu (Step 218), an indicator on the portable device (i.e., LEDdisplay 108) (Step 220), or an indicator on the portable device batterypack (Step 222). After using either of the three mediums to display thecharge status to the user (Step 216), the fast charge process 200 iscomplete (Step 224). After the fast charge process 200 is completed(Step 224), the portable device battery pack may return to normal chargemode (Step 202).

FIG. 3A illustrates a fast charge button 300 on a battery pack uponwhich the fast charge status of a battery pack may also be displayed.This button 300, when pushed, closes switch 114 (see FIG. 1) andtriggers the activation of fast charging, which allows the battery to becharged quicker than would normally be allowed. Select numbers ofpresses of the button may distinguish different functions controlledthrough switch 114. The fast charge button 300 could also be implementedthrough software allowing, for example, the use of a mouse click (seeFIG. 4C). The fast charge status of the portable device battery pack maybe displayed using a display of light-emitting diodes (LEDs) 202. FIG.3B provides a close-up view of the aforementioned fast charge button 300and LED display 302 on a portable device battery pack in accordance withthe disclosure.

FIG. 4A illustrates a model laptop have a “FAST CHARGE” button 400located on the keyboard. FIG. 4B shows a close-up view of the “FASTCHARGE” button located on the model laptop keyboard. FIG. 4C shows anexemplary pop-up window that may appear to present a user with theoption of initiating software that will perform the “fast charge” optionof the battery. Upon pressing the “FAST CHARGE” button located on thelaptop keyboard or through a menu operation of the laptop, the user maybe presented with the option of charging the portable device batterypack via standard mode or the fast charge mode. The display could showthe approximate times either mode may take. One with skill in the artwill understand that the aforementioned statements are only meant to beexemplary in nature and not to limit the scope of the present invention.

The function button brings awareness to electronic device users of theavailability of the option of fast charge—compared to the regular chargecycle offered. This button may sit on the face, side or bottom of thelaptop device to allow the user to select fast charge. The first step inthe process of using the function button is to select the fast chargeprotocol for a battery pack. Next, the user should select an “activationmode” of circuitry that activates parameters in the electronic circuithaving settings suitable for fast charging. The function button may bepositioned directly on said battery pack, on the device, in thesoftware, or any combination thereof.

The function button may be implemented with multiple portable power typedevices, such as laptop computer, cell phone, DVD player, or camcorder.The purpose of the function button is to allow the user to “fast charge”to a charge that is less than 100% in reduced time. The function buttonmay also be connected to a display that displays parametric values, suchas percentage (%) of State of Charge (SOC), time to 100% SOC, estimatedcharge to partial % SOC, and other parameters related to the user'sability to judge when it is appropriate to prematurely (meaning before100% SOC) interrupt charging sequence.

The term “switch” includes buttons, physical and display based switches,and can be in the form of knobs, toggles, and the like.

Embodiments of the present invention enable an energy-efficient mode ofpowering an electronic device and charging/discharging an associatedbattery by an associated AC adapter. The energy-efficient mode (alsoreferred to as a “green” or “eco” mode) may be initiated and terminatedby a user by actuating one or more switches (i.e., a “green button” or“eco button”) located at the battery pack, device and/or AC adapter. Theswtiches may be configured in a manner comparable to the “fast charge”switch described above. A user may enter the energy-efficient mode at aconvenient time and then returns to a normal, “fast charge” or othermode at a later time. Additional user buttons are located on the batterypack device or AC adapter which select other modes of charging ordischarging, such as fast-charge (“high performance”) or normal usagemodes. A number of system configurations enabling an energy-efficientpower mode, as well as associated methods, are described below withreference to FIG. 5A-FIG. 9C. One or ordinary skill in the art willunderstand that the electronic circuitry of FIG. 1, the method of FIG. 2and the devices illustrated in FIGS. 3A-4C may be adapted to enable anenergy-efficient power mode as described below.

A software-based GUI (Graphical User Interface) on the device enablessimilar functionality to the buttons described above. The software GUIhas the added benefit of allowing the user to adjust a selected modeover a range, similar to volume slide control in an audio systemenhancing the user control as opposed to a simple binary switchselection.

An environment-conserving energy-efficient mode of a battery packdevice, and AC adapter can be employed. Upon pressing the eco modebutton, the new energy-efficient power state is entered. The batterypack, device and AC adapter operate in a coordinated manner to increasethe overall energy efficiency of the combined system. For example,exploiting a well-known property that AC adapters run more efficientlyat higher load levels, the AC adapter would be run for a short period oftime at high load (with corresponding high efficiency), therebyfast-charging the battery pack, and then switched to an idle stand-bymode. The battery pack would then provide primary power to the systemeven though the AC adapter is still attached. At a predeterminedthreshold state of charge, the battery pack would request fast chargingfrom the AC adapter until it is again replenished.

A communication method and protocol to notify the battery pack, deviceand AC adapter of the selected energy mode (for example, ecofast-charging, high performance, or normal modes) can be employed sothat each device can be put into the desired mode even when that mode isactivated from another component in the power system. In this manner,the components of the system are enabled to work together to optimizepower use for the selected mode. For example, when the user presses theeco button on the AC adapter, the communication method will enable boththe notebook PC and battery pack to become notified that the system hasentered an energy-efficient eco mode. They will then take appropriateactions to enable energy-efficient operation, such as dimmed display,spinning down optical and hard drives or reducing processor frequency.Furthermore, important conditions of the power state may be communicatedbetween the components. For example, the battery can notify the adapterof its state of charge.

In another example, the adapter may notify the battery and the device ofits present energy conversion efficiency and provide guidance on whetherto lower, maintain or increase power consumption to improve the energyconversion efficiency.

A connector transfers power and communicates data between an AC adapterand a device or battery pack. In one possible implementation, theconnector has a combination of a standard two-conductor barrel-typeconnection for power transfer and an additional third conductor dataconnection on which a 1-wire communication protocol is implemented forthe communication method described above. In another possibleimplementation, the AC adapter, device, and battery pack may communicateusing standard wireless, infrared, or radio frequency communicationtechniques.

An indicator shows environmental conservation impact resulting from acurrently selected energy-efficiency mode. This could be, for example, agreen light indicator or numerical display that shows the equivalentamount of CO2 savings or watt-hours of electrical power conserved.

A dual, triple or higher mode multiple-wavelength light indicator fordisplaying the current power state on the battery pack, device or ACadapter can be employed. One implementation of the light indicator is atri-mode LED (Light Emitting Diode) with red (high performance mode),yellow (normal mode) and green (eco mode) colors.

A user button may activate the fast charge mode with the additionalability to cancel the fast charge mode. In this manner, a user enters afast charge mode at a convenient time and then returns to the normalcharge mode at a later time. The fast mode would increase the chargingrate to greater than the typical 0.7 C, where C is the capacity of theseries cells (for example, a charge rate between 1 C and 2.0 C).Therefore, we a user selects the fast charge mode, the charging rate maybe maintained at approximately 1.5 C or a higher rate, and when the userde-selects the fast charge mode or the machine is off, the charging ratemay be between 0.5 C to 0.7 C.

More than one external power source (i.e., AC adapter, external DCsupply—either a battery or DC/DC adapter) to the notebook may beconnected, as desired by or at the convenience of the user. For example,the notebook can support the connection of four (4) AC adapters whichcan be used to charge the notebook computer simultaneously orindependently. When a single adapter is connected, it charges thenotebook battery at the normal charge rate. If two or more independentAC adapters are connected, the notebook would have sufficient power tocharge the battery at accelerated charge rates.

A new power state for the operating system to enter (other such statesare well known and include “hibernate” and “sleep”). Upon pressing thefast charge mode button, the new fast charge power state is entereduntil a satisfactory charging condition is met (e.g., a constant currentcycle has been completed or when the battery reaches a specified stateof charge) and then the fast charge power state is deactivated by theoperating system. The new fast power state could have a variety of userselectable reduced-power behavior options for the notebook PC, such asdimmed/off display, halt optical drive motor, halt hard drive motor,reduce central processor speed, reduce graphics processing and/or reducethe amount of active system memory.

A user button activates the fast charge mode with the additional abilityto cancel the fast charge mode. In this manner, a user can enter a fastcharge mode at a convenient time and then return to the normal chargemode at a later time. Closure of the notebook lid can act as a triggerfor entering the fast charge mode or the fast charge power state. An ACadapter with enhanced charging ability triggers the notebook to enterfast charge mode using a hardware sense technique or by a softwarecommunication to the notebook (e.g., SMBus).

An IC charger includes multiple simultaneous power inputs (e.g.,charging simultaneously from an AC adapter and an external batterystorage device) and outputs to (e.g., both the notebook and notebookbattery pack undergoing fast charging). In one embodiment, a simplecircuit rectifies the AC line voltage and directly charges a stack ofcells with nominal voltage approximately equal the root-mean-square ofthe AC voltage magnitude (e.g., 120/sqrt (2) or 240/sqrt (2) V). Anotebook may be plugged directly into a POTS (Plain Old TelephoneService) circuit or POE (Power Over Ethernet) to access power from thetelephone network.

A device and associated charging circuitry may include the followingarchitecture:

-   -   1) An AC adapter—an external device that rectifies the AC line        voltage and down converts it to some lower voltage DC output        (typically in the 12-24V range)    -   2) A battery charger IC—an integrated circuit, located within a        battery pack or the notebook, which takes the DC input voltage        described above and supplies power to the notebook and/or to the        battery depending on the requirements of the system at that        time. The voltage supplied to the notebook is closely regulated        to 4.2V*N, where N is the number of cells connected in series.        The supply voltage to the system may be anywhere from 3.0V*N up        to the DC input voltage, and may be programmable via external        resistors or firmware through a communications interface.    -   3) A gas gauge and AFE chipset—these are ICs located inside the        battery pack that control whether the output of the battery        charger IC is connected to the cells.

FIG. 5A is a block diagram of a system 500 including an electronicdevice and an associated charging system supporting a plurality ofcharging modes. An electronic device 510 (e.g., a laptop computer orother portable electronic device) is coupled to a battery pack 520 andan AC adapter 530 for selectively powering the device. A PowerManagement Controller (PMC) 515 at the device 510 is configured tocommunicate with a battery management system (BMS) at the battery pack520, as well as the AC adapter 530 to manage powering of the device 510and charging and discharging of the battery pack. Such communication maybe facilitated by a system management bus (SMBUS) 545, which may extendto the AC adapter via a serial communication link 540.

Each of the battery pack 520, device 510 and AC adapter 530, or just oneor two of them, may include one or more switches 550 a-c, 551 a-c(implemented as software and/or physical interfaces) accessible to auser for initiating one or more different modes of charging the batterypack 520 and providing power to the device 510. The buttons may includeswitches 550 a-c for initiating and/or terminating an energy efficient(“eco-charge”) mode, as well as switches for initiating and/orterminating a “fast” charge mode, such as the fast charge mode describedabove with reference to FIGS. 2-4C. The system 500 is described infurther detail below with reference to FIG. 5B.

FIG. 5B is a block diagram showing the system 500 of FIG. 5A in furtherdetail. The battery pack 520 includes a battery management system (BMS)525, which regulates the charging and discharging of the battery 527(comprising a number of power cells). The BMS 525 may include some orall of the circuitry 100 as described above with reference to FIG. 1.The BMS 525 may further include one or more registers 526 configured tostore information regarding characteristics of the battery 527 (e.g.,capability of charging at a high rate during a “fast” or “eco” charge),state of charge of the battery 527, and/or an indicator of the chargemode presently selected. The BMS may facilitate charging and dischargingof the battery 527 by controlling a switch T1 (e.g., a transistor) tocontrol a corresponding circuit.

The AC adapter 530 includes an AC adapter charger controller (ACA) 535,which is configured to control operation of the AC adapter 530,including output current I_(charge), according to a selected power mode.The ACA 535 may further include a plurality of registers 536 configuredto store information regarding operation of the AC adapter 530,including operating efficiency, charge current and/or and indicator ofthe charge mode presently selected.

The electronic device 510 includes a power management controller (PMC)515, which manages power to the device 510 as well as the power mode(e.g., normal, “fast” charge and “eco” mode) as selected by a user. ThePMC 515 may include some or all of the circuitry 100 as described abovewith reference to FIG. 1. The PMC 515 controls power to the remainingcircuitry of the device (not shown) at the “primary power nodes” viaswitches T2, T3 (e.g., transistors).

The PMC 515 may be configured further to determine a selected power modeaccording to user input, and communicate with the BMU 525 and ACA 535via the system management bus (SMBUS) 545 to transition the entiresystem 500 between a number of power modes. For example, a user mayactuate one of the switches 550 b, 551 b located at the device 510 toenter either a energy-efficient (“eco”) power mode or a fast chargemode, respectively. (Alternatively, actuating a switch 550 b, 551 b mayexit a particular mode, returning to a “normal” charge mode.) Inresponse, the PMC communicates the selected mode to the BMS 525 and theACA 535, which in turn operate the battery pack 520 and AC adapter 530,respectively, according to the selected mode. Methods relating to the“fast charge” mode are described above with reference to FIG. 2; methodsrelating to the “eco” power mode are described below with reference toFIGS. 8A and 8B. Alternatively, a user may actuate a switch 550 a, 551 alocated at the battery pack, or a switch 550 c, 551 c located at the ACadapter, to enter or exit a “fast” charge mode or an “eco” power mode.In such a case, either the BMS 525 or the ACA 535 may detect theselection and communicate the same to the PMC 515 for transitioning apower mode as described above.

In further embodiments of the invention, the system 500 may include aplurality of power sources (not shown) in addition to the AC adapter530, the PMC selecting from among the power sources to charge thebattery and provide power to the device 510. Additional power sourcesmay include a DC-to-DC power adapter, external battery, an additionalAC-to-DC adapter, or another power device. In selecting among the powersources, the PMC may include logic to determine an optimal energyefficiency based on a number of inputs, including energy efficiency ofthe power sources at a given current output and a maximum current outputof the power sources. Moreover, a plurality of power sources may berecruited in combination to provide the selected high current to chargethe battery 527 at a high rate.

FIG. 6 is a chart depicting a relation between power efficiency andoperating load of an AC power adapter. The relation as shown is intendedto illustrate a general principle of efficiency versus load exhibited bysome AC-to-DC power adapters, and is not necessarily to scale, noraccurate with regard to a particular AC adapter of an embodiment ofpresent invention.

As indicated by FIG. 6, an AC adapter may exhibit much higher efficiencyin power conversion when operating at a higher load than when operatingat a lower load. As a result, different modes of operation maycorrespond to different efficiencies. With reference to the system 500of FIG. 5B, for example, when charging a battery is disabled and thedevice is powered entirely through the AC adapter, the AC adapteroperates at a low load (e.g., 50%), resulting in a lower efficiency(e.g., 87%) (1). During a normal charge (the AC adapter is providingcurrent both to charge the battery and power the device), the load atthe AC adapter is relatively higher (e.g., 75%), resulting in a higherefficiency (e.g., 93%) (2). Further, an energy-efficient (“eco”) powermode may transition periodically between two states: a first mode wherethe battery is charged at a high rate (e.g., above 1 C) and the deviceis powered by the AC adapter (3); and a second mode where charging isdisabled and the device is powered by the battery (4). As a result, an“eco” power mode provides for utilizing an AC adapter at a highefficiency while operating the device and charging the battery.

FIG. 7 is a state diagram illustrating a plurality of modes for charginga battery. In an initial (“non-charging”) state 710, a device andassociated charging circuitry (e.g., the system 500 of FIGS. 5A-B)relies primarily on an AC adapter to power the device, while the chargerremains idle, meaning that the battery is disconnected from charging ordischarging. From the initial state 710, the system may enter one of aplurality of states for charging the battery and powering the device,and enters the state in response to a user selection (e.g., actuating aswitch). In a “normal charging” state 720, the battery is charged at anormal charge current, while the device is powered by the AC adapter.When the battery is detected to have reached full charge, the batterycharger becomes idle, and the device continues to rely on power from theAC adapter (725). In the event that the AC adapter is disconnected, thedevice will transition to utilize power from the battery.

In a “fast charging” state 730, the battery is charged at a high chargecurrent, while the device is powered by the AC adapter. When the batteryis detected to have reached full charge, the battery charger becomesidle, and the device continues to rely on power from the AC adapter(735). In an energy-efficient “eco” power state 740, the battery ischarged at a charge current determined to operate the AC adapter at ahigh efficiency (e.g., a maximum safe current), while the device ispowered by the AC adapter. When the battery is detected to have reachedfull charge, the battery charger becomes idle, and the transitions todraw power from the battery rather than the AC adapter (745). As aresult, operation in the “eco” power states 740, 745 utilizes the ACadapter at a higher efficiency (see, e.g., FIG. 6).

FIG. 8A is a flow diagram illustrating a method of initiating anenergy-efficient (“eco”) power mode, which may be implemented by thesystem 500 provided in FIGS. 5A-B. Prior to initiating this mode, thesystem may be configured in a “normal charge” or other state (805). Auser initiates the “eco” power mode (806) through a graphical userinterface on a display associated with the device (810 d), or byactuating a switch on the battery pack (810 a), the AC adapter (810 b)or the device (810 c). Accordingly, the system activates the “eco” powermode (815).

At the onset of the “eco” power mode, the system may retrieveinformation regarding the operation and efficiency attainable by theconnected AC adapter (820). Such information may be available at one ormore registers at the AC adapter, and may be used to determine anoperating current for the AC adapter. Thus, an operating current knownto enable high efficiency of the AC adapter can be selected. The device(e.g., a power management controller (PMC) within the device) may thencommunicate with the AC adapter (e.g., AC adapter charger controller(ACA)) to request the aforementioned operating current to enable a“fast,” energy-efficient charge from the AC adapter (825). During thischarge of the battery, the device draws primary power from the ACadapter, further increasing the load at the AC adapter, which, in turn,may further increase the efficiency of the AC adapter.

This state of charge continues until the battery is fully charged (826).The state of battery charge may be monitored at the battery pack by thebattery management unit (BMU), which in turn may indicate the state ofcharge at a register to be read by the PMU. Upon reaching a full charge,the device disconnects the AC adapter from the primary power input,connecting the battery pack to draw power in its place (830). The devicecontinues to draw primary power from the battery until the batteryreaches a “low charge” threshold (835). In response, the system mayreturn to a “normal charge” mode (805), “eco” power mode (806) or othermode to charge the battery and continue providing power to the device.

FIG. 8B is a flow diagram illustrating a method of conducting anenergy-efficient charge mode, which may be implemented by the system 500provided in FIGS. 5A-B. The method may include one or more operations asdescribed above with reference to FIG. 8A, and may relate to operationsat the BMS 525, PMC 515 and ACA 535 described above with reference toFIGS. 5A-B.

With reference to FIG. 5B, during “normal” operation mode for poweringthe device 510 using the AC adapter 530, the PMC 515 and BMS 525 controlswitch T3 to be closed and switches T1, T2 to be open, therebyconnecting the AC adapter 530 to the primary power node to the device510 (855). In response to detecting that an “eco” mode switch isactuated (856), the PMC queries the ACA to determine whether the ACadapter 530 supports operation in the “eco” power mode (860). Thisdetermination may be made based on characteristics of the AC adapter 530(e.g., maximum current output), which may be indicated at one of theregisters 536. If the “eco” power mode is available, then the BMS 525closes switch T1 and the PMC 515 opens switch T3 and closes switch T2,thereby connecting the battery 527 to the primary power node of thedevice 510 (862). Thereafter, the PMC 515 continually or periodicallyqueries the BMS to determine whether the battery needs to be charged(865). This determination may be made by comparing a state of charge ofthe battery 527 (as indicated by the register 526) against a low-chargethreshold. If a charge is needed, then the BMS 525 and PMC 515 closeswitches T1, T2, T3, connecting the AC adapter 530 current source toboth the primary power node of the device 510 and the battery 527 (870).Further, the ADA 535 selects a high current output associated with theenergy-efficient “eco” power mode.

The battery charge may be determined to be complete when the state ofbattery charge, as indicated by the BMS 525, reaches a given threshold(875). Upon completion, the device may return to utilizing the batteryfor primary power (862), repeating a cycle of discharging the battery(865) followed by charging the battery under a high-current “eco” chargemode (870). This cycle may be repeated indefinitely provided that the“eco” switch remains actuated by a user. Alternatively, the system 500may return to a “normal” power mode, relying on the AC adapter 530 toprovide primary power to the device 510 (855)

FIGS. 9A-C are timing diagrams illustrating AC adapter current andbattery pack current during each of a plurality of charge modes.Relative current corresponds to the numbered designations shown in FIG.2, but are not shown to scale. FIG. 9A illustrates AC adapter currentand battery pack current during several cycles of an “eco” power mode asdescribed above with reference to FIG. 8B. At times 0-T1, T2-T3 and T4+,the AC adapter is disconnected from the battery pack and the device, andthus provides no current output (4). Accordingly, the battery providespower to the device, discharging the battery at a rate of 0.5 C(variable dependent on load at the device). At times T1-T2 and T3-T4,the AC adapter provides a high current output 13, providing both forcharging the battery at a rate of 1 C or greater and powering the device(3).

FIG. 9B illustrates AC adapter current and battery pack current duringseveral cycles of a “fast” charge mode. At times 0-T1, T2-T3 and T4+,charging of the battery is disabled, and the AC adapter provides primarypower to the device (1). Accordingly, there is no current output at thebattery. At times T1-T2 and T3-T4, the AC adapter provides a highcurrent output 13 (which may be equal to or distinct from the current 13provided in the “eco” power mode), providing both for charging thebattery at a rate of 1 C or greater and powering the device (3).

FIG. 9C illustrates AC adapter current and battery pack current duringseveral cycles of a “normal” charge mode. At times 0-T1, T2-T3 and T4+,charging of the battery is disabled, and the AC adapter provides primarypower to the device (1). Accordingly, there is no current output at thebattery. At times T1-T2 and T3-T4, the AC adapter provides a normalcurrent output 12, providing both for charging the battery at a “normal”rate of 0.7 C and powering the device (2).

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method of providing power to an electronic device, comprising: upondetecting a battery reaching a high threshold state of charge, enteringa first power state by switching a circuit to disable current at anAC-to-DC adapter to enable the battery to provide primary power to theelectronic device; upon detecting the battery reaching a low thresholdstate of charge, entering a second power state by switching the circuitto provide a high current at the AC-to-DC adapter to charge the batteryand provide primary power to the electronic device.
 2. The method ofclaim 1, wherein the AC-to-DC adapter charges the battery at a high ratein the second power state, the high rate being greater than 1 C.
 3. Themethod of claim 2, wherein the high rate is greater than 1.5 C.
 4. Themethod of claim 2, further comprising detecting whether the battery iscapable of being charged safely at the high rate prior to entering thesecond power state.
 5. The method of claim 1, further comprisingreturning to the first power state upon detecting the battery reaching ahigh threshold state of charge.
 6. The method of claim 1, furthercomprising alternating between the first and second power states inresponse to detecting the high and low threshold states of charge overtime.
 7. The method of claim 1, further comprising enabling the firstand second power states in response to a user selection of anenergy-efficient power mode to power the electronic device.
 8. Themethod of claim 7, further comprising entering a third power state inresponse to a user selection of a power mode other than theenergy-efficient power mode, the charge mode being one of a normal powermode and a fast charge mode.
 9. The method of claim 7, furthercomprising entering a third power state prior to the user selection byswitching the circuit to provide a low current at the AC-to-DC adapterto charge the battery at a low rate and provide primary power to theelectronic device.
 10. The method of claim 9, wherein the low rate isless than 1 C, and the high rate is greater than 1 C.
 11. The method ofclaim 9, wherein the AC-to-DC adapter operates at a higher energyefficiency at the high current than at the low current.
 12. The methodof claim 1, further comprising detecting whether the AC-to-DC adapter iscapable of providing the high current prior to entering the second powerstate.
 13. The method of claim 1, wherein the battery is a lithium ion(Li-ion) battery.
 14. The method of claim 1, further comprisingselecting a rate of the AC-to-DC adapter current output based oncharacteristics of the AC-to-DC adapter and characteristics of thebattery.
 15. The method of claim 14, wherein the characteristics of theAC-to-DC adapter include a maximum current output, and thecharacteristics of the battery include a maximum safe charge rate. 16.The method of claim 14, wherein the characteristics of the AC-to-DCadapter include a predicted energy efficiency corresponding to a givencurrent output.
 17. The method of claim 1, further comprising selectingamong a plurality of AC-to-DC adapters to provide the high current inthe second power state, the selection being based on an indication ofmaximum output current at each of the plurality of AC-to-DC adapters.18. The method of claim 1, further comprising selecting among aplurality of power sources to provide the high current in the secondpower state, the selection being based on an indication of maximumoutput current at each of the plurality of power sources, the powersources including one or more of an AC-to-DC adapter, a DC-to-DCadapter, and an external battery.
 19. The method of claim 18, whereinthe selection is based on energy efficiency corresponding to a givencurrent output at each of the plurality of power sources.
 20. Anapparatus for providing power to an electronic device, comprising: apower circuit configured to enable and disable power to the electronicdevice from a battery and an AC-to-DC adapter; a controller coupled tothe power circuit and configured to transition between first and secondstates, the first state including disabling current at the AC-to-DCadapter and enabling the battery to provide primary power to theelectronic device in response to detecting a high threshold state ofcharge, the second state including enabling the AC-to-DC adapter toprovide primary power to the electronic device and charging the batteryin response to detecting a low threshold state of charge.
 21. A systemfor providing power to an electronic device, comprising: a batteryconfigured to provide power to an electronic device; an AC-to-DC adapterconfigured to provide power to the electronic device; and a controllerconfigured to transition between first and second states, the firststate including disabling current at the AC-to-DC adapter and enablingthe battery to provide primary power to the electronic device inresponse to detecting a high threshold state of charge, the second stateincluding enabling the AC-to-DC adapter to provide primary power to theelectronic device and charging the battery in response to detecting alow threshold state of charge.